Control device



K. CLARK CONTROL DEVICE April 26, 1938.

Filed Feb. 17, 1937 2 Sheets-Sheet l K R. S Mmmm L M VC uw WU.. m., N E K K. `CLARK CONTROL DEVICE Filed Feb.' i7, 1937 2 Sheets-Sheet -2 INVENTOR. KENDHLL CLHRK BY ne im A TORNEYS.'

Patented Apr. 26, 1938 coN'raoL DEVICE Kendall Clark, South Bend, Ind., assigner to International Engineering Corporation, Chicago,

Ill., a corporation y Application February 17,

of Illinois 1937, Serial No. 126,121.

11 calms. (C1200-iss) This invention relates to control devices such as switches, and is illustratedl as embodied in automatic switches used to control a heating system. a

An object of the invention is to provide a simple and reliable control switch or the like having a snap action, and which is preferably provided with magnetic means to providev such a snap action. Various features of novelty relate to the arrangement of the magnet and a ilat spring 'carrying the magnet armature, and which is preferably either itself a thermostat or controlled by a thermostat or a pressure device or other automatic means, and to the arrangement of the magnet and its associated parts to facilitate adjusting the air gap of the magnet, preferably by shifting the pole piece of the magnet.

'I'he above and other objects and features of the invention, including various novel combinations of parts and desirable particular constructions and arrangements, willv be apparent from the following description of the illustrative arrangements shown in the accompanying drawings, in

which:

Figure l is a front elevation of an embodiment of my invention adapted'to serve as a room thermostat to control a furnace; s

Figure Z is a central vertical section therethrough; K

Figure 3 is a horizontal section therethrough, on the line 3-3 of Figure 2;

Figure 4 is a perspective view of a cam member used in adjusting the device of Figures 1 3;

Figure 5 is an enlarged section through the end of the thermostatic spring and the magnet armature carried thereby; y

Figure 6 is a diagram of an oil burner circuit including the control device of Figures 1-3;

Figure '7 is an elevation of a modification of my invention adapted to serve as a temperative controlled safety limit switch for hot water heating systems;

Figure 8 is a front elevation of the device of Figure 7; Figure 9 isa vertical section of an embodiment intended for use as a pressure-controlled safety l limit switch for steam heating systems; and

Figure 10 is a vertical section of another thermostatically controlled embodiment, adapted for use as a temperature controlled safety limit, switch for a hot air heating system.

The embodiment of Figures 1-3 is intended for use as the room thermostat of an oil burner. system. For, example an oil burner I8 (Figure 6) and its control I2 may be connected in series between line wires i4 and I6 with such a room thermostat switch, indicated at I8, and one or more safety limit switches 20,

which may be of the form hereinafter described.

The illustrated room cludes a vertical base 22,

thermostat switch inadapted .to be secured to a wall and having a conduit 24 for the lead-in wires;

A suitable removable cover sired, have a thermometer 28 mounted thereon.

The base 22 support 30, between the mounted plates or brack ing material.

has mounted thereon a U -shaped arms of which are ets 32and 34 of insulat- T'hese brackets carry the operating which may be inclosed in a strip 36 of insulating material.

A large screw 38 is formed with a ing oneside oi the supp threaded to receive a clamp other side of the support; a screw 42 in its end which head engagort 32, and is externally nut 40 engaging the it is provided with forms a binding post for one of the lead-in wires. The large screw 38 acts as a guide or journal to slidably support `a small permanent magnet 46 (preferably made of high permeability alloy) carried by a sleeve 48 carried by the screw 3 The sleeve 48 has ri 8. gidly secured thereto a tube 50 'of insulating materiahformed with a flange 52 projecting through an opening 54 in the cover 28, and graduated in temperatures to eooperate with a pointer sleeve 48 has mounted 56 on thecover 28. The

thereon a `cam follower part such as a pin 58 engaging a helical cam surface on the edge of a 60, arranged'coaxially 38 and the sleeve between the magnet 46 cylindrical cam member with respect to the guide 48. A spring 62 compressed and the guide 38, holds the follower 58 yieldingiy against the cam 88 and, as the spring is preferably edge-wound of fiat stock, provides goodelectrlcal conductivity between the large screw 38 To provide for calibration,

Figure 4) as a split sleeve in the bracket 34 and having the cam 80 (as shown in seated in an opening lugs 63 embracing the The wall of the opening the magnet 46.

I preferably form bracket between them. in the bracket 34 may be serrated, for interlocking engagement with a sharp edge turned outwardly Thus may be compressed with the tween the lugs 63. strument, the sleeve on the cam 80 bein calibrating the infingers androtated, and when released it ex-A pands and grips the bracket 34.

The armature oi' the magnet iron plate 66, secured to spring 88 by a steel rive of silver or the like, and

is shown as a soft the end of a looped at t 10 having a plating 12 the plated head of which engages the magnet 46 when the circuit is closed. The spring 66 in this case is bi-metallic, and

forms the thermostatic element of the switch. It preferably has two or more loops, and is flxedly held on the bracket I2 by a nut 14 threaded on 'a bolt 16 passing through the bracket, and the head of which carries a binding post I0 for the other lead-in wire.

Assuming that the armature is away from the magnet, and that thetemperature in the room gradually falls to the temperature for which the device is set, as indicated by the scale on the flange 52, the lowering of the temperature fiexes the bimetallic spring 68, until the gap between the amature and magnet 46 becomes small enough forthepullof the magnet to overcome the resistance of the spring 68, whereupon the armature suddenly snaps into engagementwith the magnet, thus closing the circuit.

As' the temperature rises, the spring 68 exerts more and more tension on the armature, in a direction to open the circuit, until when it overbalances the pull oi the magnet the armature suddenly snaps to open position. 'I'he snap action in opening and closing depends on the fact that the pull of the-magnet increases rapidly as the air gap is diminished, and decreases rapidly as the air gap is increased, so that at some critical point in both opening and closing the magnet will either suddenly close its circuit with the amature, or will suddenly release the armature.

As previously mentioned. the device may be calibrated at the factory by turning the cam 60 about its axis. i

The device shown in Figures 7 and`8 is adapted for use as a safety limit switch for a heating system enclosing hot water as a circulating medium, although it may be used wherever a circuit is to be opened or closed as a predetermined temperature is reached in a conduit or the like. 'I'he illustrated switch is intended for use as the switch 20 in Figure 6 and serves to open the circuit when the circulating hot water in a pipe 04 exceeds a predetermined safe limit, and, .of course, to close the circuit when the temperature falls below that limit after the burner stops. 'I'he various parts which are the'same as, or very closely similar to, those in Figures 1-3 are indicated by the same reference characters increased by 100. It is believed that the operation of these parts will be apparent without extended description.

The base |30 in this case is curved to fit closely against the pipe 84, or the equivalent part whose temperature is to control the device, to which it is secured by a clamp such as metal straps 06 drawn together by a bolt 08. As the thermostatic element |68 in this case must be quite sensitive, its free end (with the magnet armature) is supported by a vertical ilat spring fixed to thebase |30 at its lower end. The ilat spring 90 is attached to the amature through a section 92 of insulating. material, to avoid possible grounding of the circuit on the conduit V04, and a strip 94 of insulating material may be interposed between the bimetallic element |60 and the spring 90.

The snap action.in opening andclosing the switch, under the control of the bimetallic element |60 as it is aiiected by the temperature, is as previously described.

In Figure 9 the device is shown modied to be controlled by pressure, for example as a boilercontrolled safety limit switch. Most of the parts are the same as in Figure 8, and are indicated by the same reference characters. However, the

spring 260 is a simple flexible ilat spring, and is not bimetallic like spring |60. The spring 290 is looped aroundat its lower end, instead of beihg straight like the spring 99, and has a depression to receive the rounded endof a thrust plunger 96 passing through the base |30 and having a mushroom head 98 which backs up a diaphragm |00 in a chamber |02 having an inlet |04 adapted to be connected to the space whose' pressure is to control the switch.

In this case the controlling pressure acts through the plunger 9B to bend the spring 290 near the point at which it is secured to the base i30 thereby tending to swing the contact end of the spring 290 toward the base and away from the magnet |46 to break the circuit as the spring force overcomes the magnetic force. When thel pressure decreases the contact end swings back until it comes within thel magnetic field sumciently to be snapped back into contact.

The construction of Figure 10 is the same as that in Figure 8, except that instead of using the spring |68 of bimetallic thermostat material,

it is a simple fiat spring 268 as in Figure 9, the thermostatic action being due to engagement with the spring 90 of a thrust rod or plunger |66 (preferably of brass) secured at its outer end to a tube |08 of dissimilar metal, i. e. a metal having a different coefficient of expansion (preferably invar). This modification is adapted to be used as a safety limit switch in a hot air heating system to prevent overheating the furnace by opening the burner control circuit when the circulating air from the heater exceeds a predetermined safe linut. l

The rod |06 and tube |09 are inclosed in a tubular housing ||0 adjustably held by a ball Il! mounted in a socket formed half in the wall of the hot air pipe or conduit ||4 and half ina stamping ||6 attached thereto. The tubes |06 and I I0 are shown threadedly connected to a boss on the base |30, and the plunger |06 slides-- through a bearing in this boss at one end and is slidably supported at its other end by a washer H6 of nonmetallic material which is seated in the end oi the tube |0.

If the switch is to open on a rise in temperature as required for safety limit control, tube |00 has a greater coeflicient of expansion than plungerl |06; the reverse is true if the switch is to close on a rise in temperature,

While several illustrative embodiments have been described in detail, it is not my intention to limit the scope of my invention to those particular embodiments, or otherwise than by theand means operated by turning the sleeve on the guide for shifting the magnet to vary the gap between the magnet and said armature.

2. A, switch comprising a guide, a movable magnet, a'sleeve surrounding the guide and carrying the magnet, a contact having associated therewith an armature attracted by the magnet, a spring carrying the contact and armature and urging them away from the-magnet and having associated therewith meansifor bending the spring toward the magnet until its attraction for the armature overcomes the resistance of the spring..and means operated by turning the sleeve on the guide for shifting the magnet to vary the gap between the magnet and said armature.

3. A switch comprising a guide, a movable magnet, a sleeve surrounding .the guide and carrying the magnet, a contact yieldingly urged away from the magnet therewith an armature attracted by the magnet, a stationary cam member coaxial with respect to the magnet and having a generally helical cam surface, and a follower part carried by the sleeve and engaging the cam surface.

4. A switch comprising a guide, a .movable magnet, a sleeve surrounding the guide and carrying the magnet, a contact having associated therewith an armature attracted by the magnet, a spring carrying the contact and amature and urging them away from the magnet and havingassociated therewith means for bending the spring toward the magnet until its attraction for the armature overcomes the resistance of the spring, a stationary cam member coaxial with respect to the magnet and having a generally helical cam surface, and a follower part carried by the sleeve and engaging the cam surface.

5. A switch comprising a guide, a movable magnet, a sleeve surrounding the guide and carrying the magnet, a contact yieldingly urged away from the magnet and having associated therewith an armature attracted by the magnet, a stationary cam member coaxial with respect to the magnetA and having a generally helical cam surface, a follower part carried by the sleeve and engaging the cam surface, and a spring compressed between the guide and the magnet $5 urging said part against the cam surface.

6. A switch comprising a guide, a movable magnet, a sleeve surrounding the guide and carryving the v magnet, a contact having associated therewith an armature attracted by the magnet, 40 a spring carrying the contact and amature and urging them away from the magnet and having associated therewith means for bending the spring toward the magnet until its attraction for the armature overcomes the resistance of the spring,

. a stationary cam member coaxial with respect to the magnet and having a generally helical cam surface, a follower part carried by the sleeve and I,engaging the cam surface, and a spring' compressed-between'the guide and the magnet and urging said part against the cam surface.

7. A switch comprising a guide, a movabley magnet, a sleeve surrounding the guide and carryl ingthe magnet, a contact yieldingly urged away from the magnet and having associated therewith an armature attracted by the magnet, a stationary cam member coaxial with respect to the magnet andhaving a generally helical cam surface, and a follower part carriedby the sleeve and' engaging the cam surface, said cam member havo ing a mounting permitting it to be turned about its axis to adjust the'position of the ca m surface.

8. A switch .comprising a guide', a movable magnet, a sleeve surrounding the guide and carrying the magnet, a contact having associated therewith an armatureI attracted by the magnet,

a spring carrying the contact and amature and urging them away from the magnet'and having associated therewith means for bending the spring toward the magnet until its attraction for the amature overcomes the resistance of the spring, a stationary cam member coaxial with respect to the magnet and having a generally helical cam surface, a follower part carried by the sleeve and engaging the cam surface, said ca m member having a mounting permitting it to be and having associated' and turned about its axis to .adjust the position of the cam surface.

9. A magnet assembly for a switch orthe like 4comprising a magnet yieldingly urged in one direction and having attached thereto a member having a cam-engaging part, and a stationary cam engaged by said part and determining the position of the magnet.

10'. A magnet assembly for a switch or the like comprising a magnet yieldingly urged in one direction and having attached thereto a rotatable member carrying a cam-engaging part, and a stationary cam having a helical cam surface engaged by said part and determining the position of the magnet.

1l. A magnet assembly for a switch or the like comprising a magnet yieldingly urged in one direction andV having attached thereto a rotatable ,member carrying a cam-engaging part, a stationary cam having a helical cam surface engaged by said part and determining the position of the magnet, and a support in which the cam is rotatably mounted to permit adjustment.

12.' A magnet assembly for a switch or the like comprising a magnet yieldingly urged in one direction and having attached thereto a rotatable member carrying a cam-engaging part, a bracket .having an opening coaxial with respect to said member, and a cylindrical cam having one edge formed as a helical surface engaged by said part and which is seatedin said opening for angular adjustment therein and which has means engaging the bracket and holding the cam in adjusted position.

13. A magnet assembly for a switch or the like comprising a magnet yieldingly urged in one direction an'd having attached thereto a rotatable member carrying a cam-engaging part, a bracket having an opening coaxial with respect to said member,`and a cylindrical cam having one edge formed as a helical surfacefengaged by said part and which is seated in said opening for angular adjustment therein and which hasa tooth engaging and interlocking with the opening wall and holding the cam in adjusted position.

14. 'A switch comprising a support, a guide mounted at one end on the support and projecting therefrom and which has movably mounted thereon a permanent magnet, means sleeved' about the guide and movable about its axis to adjust the magnet, Ya bi-metallic thermostat formed as a looped fiat spring and which -is mounted at one end on the support and which carries at its otherend an armature opposite the magnet, and electrical connections tothe magnet and the thermostat respectively.

15. A switch comprising `a support which has mounted thereon a permanent magnet, a bimetallic thermostat formed as .a looped flat spring and which is mounted at one end on the support and which carries atits other end an armature opposite the magnet, and electrical connections to the magnet and the thermostat respectively. A

16. A switch comprising a support, a guide mounted at one end on the support and projecting therefrom and which has movably mounted thereon a permanent magnet, means sleevedl about the guide and movable about its axis to adjust the magnet, a looped flat spring mounted at one end on the support and having at its other end an armature cooperating with the magnet, anelectric circuit opened and closed by movements of the armature, another flat spring secured to the armature at one end and fixed at its opposite end, and control means acting on said other spring.

17. A switch. comprising a support, a guide mounted at one end on the support and project- V ing therefrom and which has movably mounted thereon a permanent magnet, alooped fiat spring mounted at one end on the support and having at its other end an armature cooperating with 

